Suction box covers with rows of drainage openings for uniform dewatering

ABSTRACT

THIS INVENTION RELATES TO SUCTION BOX COVERS, AND A METHOD FOR PRODUCING THEM, FOR USE IN UNIFORMLY DELIQUIFYING A WEB ON A TRAVELING FORMING MEDIUM, FOR EXAMPLE IN PAPERMAKING MACHINES; THE COVERS HAVING A PLURALITY OF DRAINAGE OPENINGS OF RADIUS R ORIENTED IN UNIFORMLY SPACED PARALLEL ROWS, THE OPENINGS IN ADJACENT ROWS BEING SPACED FROM EACH OTHER IN THE CROSS-MACHINE DIRECTION A CENTER TO CENTER DISTANCE. A FROM THE NEXT ADJACENT OPENING. N CONSECUTIVE ROWS OF SAID OPENINGS FORMING A REPETITIVE PATTERN, SAID SPACING A BEING DETERMINED BY THE EQUATION:   D R A W I N G

July 27, 1971 R. WALSER 3,595,141

SUCTION BOX COVERS WITH ROWS OF DRAINAGE OPENINGS FOR UNIFORM DEWATERING Filed sept. zo. 196s 3 Sheets-Sheet 1 (A7055 Mms/VE July 27, 1971 R. wALsER 3,595,747

sucTIoN Box covERs WITH Rows 0F DRAINAGE oPENINGs Fon UNIFORM DEWATERING Filed Sept. 30, 1968 3 Sheets-Sheet 2 l l l .2a 2'2 2'4 .6 25 a 2 4 55 55 INVIA/Toa q /fl/ (P055 ,Pz/06% Pf/ Muff/P M45/mvg F l (5.5 e //Pffr/@A/ WM,

July 27, 1971 R. wALsER 3,595,747

SUCIION BOX COVERS WITH ROWS OF DRAINAGE OPENINGS FOR UNIFORM DEWATERING 3 Sheets-Sheet l Filed sept. 3o. 196e Fl G. 9 @P0/afnam @FA fam? ww @1mm/v United States Patent O 3,595,747 SUCTION BOX COVERS WITH ROWS OIF DRAIN- AGE OPENINGS FOR UNIFORM DEWATERING Rudolph Walser, Delmar, NY., assigner to Huyck Corporation, Rensselaer, NY. Continuation-impart of abandoned application Ser. No. 561,936, .lune 30, 1966. This application Sept. 30, 1968, Ser. No. 767,049

Int. Cl. D21f 1/48 U.S. Cl. 162-374 '7 @Claims ABSTRACT OIF THE DISCLOSURE This invention relates to suction tbox covers, and a method for producing them, for use in uniformly deliquifying a web on a traveling forming medium, for example in papermalcing machines; the covers having a plurality of drainage openings of radius R oriented in uniformly spaced parallel rows, the openings in adjacent rows being spaced from each other in the cross-machine direction a center to center distance of A from the next adjacent opening, N consecutive rows of said openings forming a repetitive pattern, said spacing A being determined by the equation:

BACKGROUND OF THE INVENTION 'Ihis application is a continuation-in-part of co-pending application Ser. No. 561,936, filed June 30, 1966, now abandoned.

The present invention relates to papermaking machines and more specically to suction boxes suitable for use in such machines.

In the so-called Fourdrinier machine, the use of which is well known in the paper manufacturing art, an aqueous suspension of cellulose, mineral, or other fibers (called the furnish) is fed on a moving forming medium, which usually is a woven, screen-like endless belt made from metal and/or synthetic filaments, to produce a web of paper, paperboard, pulp, or similar sheet-like material. In such a system, the web is carried by the forming medium, in a-direction hereinafter referred to as the machine direction, past dewatering devices in order to remove water from the web before it is transferred to the press section of the papermaking machine, 'where the nips formed by adjacent press rolls further remove water from the web.

The dewatering devices commonly used in the forming section of the papermaking machine include suction boxes. Each suction box has a cover with a plurality of drainage openings formed therein; the drainage openings being of varying sizes and configurations and providing means for drawing water from the web. A partial vacuum is maintained in each suction box and provides the force necessary to draw the water from the web. Since the perforated cover of the suction box is disposed beneath the forming medium, the suction is, in effect, applied to the web through the forming medium, thereby causing water to be extracted from the web.

If the drainage openings in the suction boxes are not properly oriented with respect to each other, a nonuniform moisture profile of the web in the cross machine direction, the direction transverse to the machine direction, will result.

This problem becomes especially critical when it is a requirement that the paper be of a uniform composition. For example, wet streaking, the term used to define ice the result of such nonuniform dewatering, can be critical in the making of electrical condensor paper since problems arise in the impregnation of the paper if it is of nonuniform density.

Therefore, one object of the present invention is to provide a means for producing a web of uniform composition.

Another object of the present invention is to provide a means for uniformly deliquifying materials which are sheet-like in form.

Another object of the present invention is to provide a means for preventing wet streaking of paper and paper-like materials.

Still another object of the present invention is to provide a suction box which unifonnly dewaters material passing thereover.

A still further object of the present invention is to provide a suction box for a papermaking machine which uniformly dewaters material passing thereover.

SUMMARY OF THE INVENTION In one embodiment of the present invention there is included a suction box, a cover having a plurality of rows of drainage openings therein; each opening being of radius R. Each of these drainage openings is spaced from adjacent openings in the same row by a center to center distance of A, and N number of rows are used to form any desired repetitive pattern of openings. This arrangement provides, as nearly as is possible, uniform dewatering of a material passing thereover and is accomplished by providing a spacing arrangement of the drainage openings in the cross machine direction in accordance with the solution to the following equation:

Additional objects and advantages of the present invention together with a better understanding thereof may be had by referring to the following detailed description of the present invention together with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. l shows a plan view, partially cut away, of a portion of a papermaking machine in which the present invention is incorporated;

FIG. 2 shows a top view of a portion of a suction box cover constructed in accordance with the principles of the present invention;

FIG. 3 shows a typical drainage way curve for a two row repetitive pattern of drainage openings;

FIG. 4 shows the various drainage way curves for various A/R relationships of a two row repetitive pattern of drainage openings;

FIG. 5 shows the maximum and minimum drainage way lengths for various A/R relationships for a two row repetitive pattern of drainage openings as well as a uniformity relationship therefor;

FIG. 6 shows a projected view of a two row repetitive pattern of drainage openings spaced at the optimum distance for maximum uniformity of drainage;

FIG. 7 shows a projection of a five row repetitive pattern of drainage openings at optimum spacing for maximum uniformity of drainage;

FIG. 8 shows a projection of a live rofw repetitive pattern of drainage openings spread apart so that the center to center distance of adjacent openings is greater than the optimum spacing; and

FIG. 9 shows a projection of a four row repetitive pattern of drainage openings at optimum spacing for maximum uniformity of drainage.

Referring now to FIG. l, there is shown'a typical arrangement in the forming section of a fourdrinier papermaking machine Ain ywhich a web of material is formed on a traveling endless foraminous belt, or forming medium, while a liquid is uniformly removed from the web. Specifically, there is shown a forming section 1 of a papermaking machine including an endless traveling forming medium 3 on which a web of material 5 in sheet-like form, such as cellulose and/or mineral fibers in a water saturated condition, is placed. The forming medium 3 is mounted over a breast roll 6 and a coach roll 8, as well as a plurality of carrier rolls 7, some of which are spring biased to ensure that proper tension is maintained on the forming medium 3.

The forming medium 3 is generally an endless belt on to which the aqueous suspension of cellulose and/or mineral fibers is disposed and may comprise an all-metal composition, all-synthetic composition such as found in Holden-Schiff-US. Pat. 2,903,021, a combination of metal and synthetic materials, or any other suitable material which provides satisfactory results, such as a perforated sheet of metal or plastic material. After being placed on the forming medium 3, the aqueous suspension is first dewatered by means of a plurality of hydrofoils 9 arranged to contact the underside of the forming medium 3. Although hydrofoils have been found to provide superior results in most instances, table rolls or the like may also be utilized for this purpose.

After the web passes through the hydrofoil or table roll section, it is ready to be more thoroughly dewatered. This is done just prior to the Web passing to the press rolls 10 and it is at this time, in particular, that care must be exercised to ensure that the web is uniformly de- Watered in order to prevent Wet streaking of the paper.

To accomplish uniform dewatering of the web, the present invention provides one or more suction boxes 11. Each suction box 11 includes a cover 13 having a plurality of drainage openings 15 therein. The suction boxes 11 are placed beneath the forming medium 3 and may optionally have a drive or power belt 17 such as shown in U.S. Pat. No. 3,222,246-Lee, disposed between the suction box cover 13 and the forming medium 3 to aid in driving the forming medium 3 with the web 5 thereon through the region of the suction boxes 11. A suction, typically on the order of 12 inches of mercury, is present in each suction box and provides the force necessary to draw water from the aqueous solution.

Although generally constructed of wood, the suction box covers may also be formed of ceramic or other materials having hard glaze finish, the stainless steels, metals such as the stainless steels with or without a hard surface finish, plastics such as the high density polyethylenes, or any other suitable material ywhich permits travel of the forming medium thereover with relative ease. The drive belt v 17 may comprise a reinforced rubber belt having a plurality of holes therein, a woven synthetic member Iwhich may be of a single layered construction, or any other suitable means. It should -be noted that the present invention is not to be limited by the specific materials heretofore cited, that they are given only as examples of materials which have been found to provide satisfactory results.

DESCRIPTION OF PREFERRED EMBODIMENT If the degree of suction exerted on the web at each drainage opening is identical, then the amount of dewatering of the web is a direct function of the time a given lpoint on the web is subjected to the negative pressure of the suction. Since all points on the web and the forming medium travel at the same rate of speed over the suce'rally displaced point on the forming medium as it travels in the machine direction, may be varied by the degree of spacing of the openings. Thus, in order to uniformly dewater a material, the drainage openings should be spaced so that the sum of the chord interceptions `in all of the drainage ways are as nearly uniform, one to the other, as is possible.

In order to accomplish thisv uniform dewatering, and referring now to FIGS. 2 and 3, there is shown a suction box cover 13 in which the drainage openings 15 are arranged in parallel rows extending in the cross machine direction, with any desired number of rows forming a repetitive pattern. In this instance, and in order to facilitate discussion of this device, there is shown only a two row repetitive pattern; i.e., a two row hole pattern which, if repeated, as is the case in FIG. 2, would be done so systematically, as described hereinafter. FIG. 2 depicts a first two row repetitive pattern and the first row of a second similar two row repetitive pattern. From FIG. 2 it can be seen that the Centers of the drainage openings in the first row of the second two row repetitive pattern are aligned in the machine direction with the centers of the drainage openings in the first row of the first two row repetitive pattern. In addition, it can be seen that an imaginary line drawn through the center of all of the corresponding drainage openings, as, for example, through the center of the rst drainage opening in each of the cross machine direction rows which form the first two row repetitive pattern depicted in FIG. 2, is angularly aligned with reference to the machine and cross machine direction, thereby forming a plurality of angularly disposed parallel rows of drainage openings. Finally, it can be seen from FIG. 2 that each drainage opening is uniformly spaced from adjacent openings in the same row. Although FIG. 2 depicts a two row repetitive pattern, it should be understood that the same alignments and equalities noted above hold true for repetitive patterns comprising any number of rows N; i.e., l, 2, 3 N where N rows form a repetitive pattern. In addition, it should be understood that a repetitive pattern may be repeated, and in the case of a two row repetitive pattern probably Would be repeated, more than twice. For example, a suction box cover may comprise ten two row repetitive patterns in lwhich case there would be twenty parallel cross machine direction rows. When this occurs, the same principles set forth herein apply; e.g., corresponding centers of the drainage openings in the first row of each repetitive pattern will be aligned in the machine direction one with the other, the center of each opening will be angularly aligned, with reference to the machine and cross machine direction, with the centers of corresponding drainage openings in each repetitive pattern, thereby forming a plurality of angularly disposed parallel rows, and each drainage opening will be uniformly spaced from adjacent openings in the same row. Accordingly, it should be understood that the present invention is not, by the description which follows, to be limited to a two row repetitive pattern device.

In order to further facilitate this discussion, each drainage opening is spaced from the next adjacent opening in the same cross machine direction row at a center to center distance of A, and each drainage opening is of a radius R.

Turning now to FIGS. 4 and 5, there is shown a graphic illustration of the effect on the drainage way patterns for various spacings of drainage openings. In particular, each curve in FIG. 4 represents a two two repetitive pattern with a certain spacing A/R of drainage openings, and shows the drainage way relationships for various A/R ratios for the two row repetitive pattern hereinafter described. From this graph, it can be seen that if the openings in adjacent rows are just tangent to each other, there is a high degree of nonuniformity. Further, it can be seen that by increasing the center to center distance A between adjacent drainage openings, the degree of nonuniformity becomes less until at some point it begins to increase; ultimately the spacings being so wide that there is no overlap in the interception between rows. By varying the center to center distance A between adjacent drainage openings, the length of chord intercepted along lines oriented in the machine direction, i.e., along each drainage way, is also varied, until the point is reached Where the summation of chord interception in any one drainage way is substantially equal to the summation of the chord interception in any other drainage way. It is at this point that uniformed liquiication will occur.

FIG. reveals a uniformity plot of the graph shown in FIG. 4. More specifically, the maximum and minimum drainage ways are plotted for the various A/R spacing ratios plotted in FIG. 4. Also shown in FIG. 5 is a curve representing the ratio of the maximum and minimum drainage ways for each spacing ratio; this being called the uniformity coeicient. From this plot it can be seen that the uniformity coeicient for a two row repetitive pattern is a minimum at an A/R ratio of approximately 3.45.

Thus, for a two row repetitive pattern, if adjacent drainage openings in the cross machine direction are spaced at a center to center distance A equal to approximately 3.45R, then the most nearly uniform dewatering will occur. Similarly, it can be seen that for a three row repetitive pattern, the most uniform dewatering will occur at a center to center spacing A equal to approximately 2.77R. However, it can be shown from a graph similar to the one shown in FIG. 5 that the uniformity coeficient for a three row repetitive pattern does not change signiiicantly between the range A=2.4R and A=2.85R.

Looking at FIG. 6, which is a projection of FIG. 3 with the drainage openings superimposed on a single horizontal axis and spaced at the optimum distance; that is, the openings are positioned in order to obtain the highest degree of uniformity, it can be seen that the drainage ways are a maximum at X/R equal 0, 0.85, and 1.73 and a minimum at X/R equals 0.7 and 1.0 From FIG. 4, it can be seen that the maximum value of the drainage ways at the maximum points is 2R; thus the common chord length of the intercepting circles shown in FIG. 6 will be equal to R. Using basic trigonometry, it is found that and by solving for A, it can be seen that A is equal to or approximately 3.46R, which is exactly what was found by graphically determining the optimum value of A.

Using identically the same method, it can be shown that the optimum spacing for a three row repetitive pattern of drainage openings is found by solving the equation:

arMRZ-eH-er Again solving for A, it can be seen that A is equal to approximately 2.766R.

If this work is carried out for successively greater repetitive row patterns, it can be seen that the following general equation results:

where R is the radius of the drainage openings, A is the center to center spacing of adjacent openings in a given row, and N is the number of rows in a desired repetitive pattern, thus, it can be seen that when the drainage openings are positioned in accordance with the above-mentioned equation, the most nearly uniform dewatering prole in the cross-machine direction will occur.

From the previous general equation, it can be seen that as the number of rows in a repetitive pattern becomes greater, the optimum spacing gradually approaches to 2R.

However, due to practical design requirements such as maintaining structural stability and the like, it is often desirous to maintain a Web distance; that is, the distance between adjacent drainage openings at least equal to R so that the minimum A is approximately 3R.

Although this is not a problem for a two row repetitive pattern, as A is equal to 3.45K, this can become a problem for repetitive patterns having more than two rows in each sequence. For intsance, a five row repetitive pattern has been found to have optimum spacing when A is equal to 2.39R. `From the above discussion, it can seen that, practically speaking, this arrangement may not be desirable since the drainage openings may be too close together. Therefore, referring now to FIGS. 7, 8 and 9, it will be seen that if an optimumly spaced five row repetitive pattern is spread apart, that is, if the distance between adjacent openings is increased, it can be shown that the pattern can be made to possess the characteristics of a repetitive pattern comprising a lower number of rows. Thus, varying the spacing of the drainage openings beyond that optimum distance, an N row repetitive pattern of openings can be made to operate as a P row repetitive pattern where P is any number less than N. The further apart the openings are spread, the lower the number of rows P the N row repetitive pattern acts.

This is illustrated by looking at FIG. 7 where there is shown a projection of a tive row repetitive pattern of drainage openings spaced at the optimum distance. Note that the points Z-Z are the inner interceptions of the outside circles with the horizontal axis.

Now looking at FIG. 8, there is shown a projection of the ve row repetitive pattern of drainage openings shown in FIG. 7 which have been spread apart so that they are spaced a distance greater than the optimum distance as calculated by the general formula. It should be noted that in IFIG. 8 while the points `ZZ are the same relative points as in FIG. 7, there is an additional pair of circles which intercept the horizontal axisI between these points; whereas in FIG. 7 no other circles intercept the axis between these points.

Referring now to FIG. 9, there is shown a projection of a four row repetitive pattern of drainage openings spaced at optimum distance. By comparing FIG. 8 with FIG. 9, it can be seen that if the openings of the ve row repetitive pattern shown in FIG. 8 are spread far enough apart, the drainage way characteristics can be made identical with those of the four row repetitive pattern shown in FIG. 9. That is, a ve row repetitive pattern of 'drainage openings now operates exactly as a four row repetitive pattern where the four row pattern is at optimum spacing.

If the openings in FIG. 8 are spread still further apart, the ve row repetitive pattern can be made to act as a three row repetitive pattern and even a two row repetitive pattern. Thus, by starting with an N row repetitive pattern, the N row pattern can be made to operate as a P row repetitive pattern by merely spreading the drainage openings of the N row pattern a distance greater than the optimum distance.

By graphic determination, it can be shown that the upper limit of ANP is shown by the :formula:

ZRN

where ANP is the maximum spacing between adjacent openings for which an N row repetitive pattern will behave as a P row repetitive pattern.

Thus, where it is desired to use, for example, a sixteen row repetitive pattern of openings, it can be seen that the optimum spacing for these holes is 2.1R. However, as noted above, the practical design requirement for the suction box cover may require that the web distance between adjacent holes be at least equal to R in order to have structural integrity. If such is the case, the pattern may be spread to a point at which there is at least the desired web ANP:

7 distance between adjacent openings. By setting the fraction equal to the minium distance or 3R, the distance the openings must be spread in order to provide maximum uniformity can be found. Note that P cannot be a fraction as all patterns must be whole numbers. For example, taking the case of a, sixteen hole repetitive pattern, it can be shown that the practical requirement for the web distance as previously mentioned, is not satisfied until P is made equal to 11. That is, the above mentioned fraction is not made equal to 3R until P is successively reduced from N until it reaches a value of 11. When this occurs, then P is the number of effective rows in a repetitive pattern an N row repetitive pattern will actually act as. From this, it is then seen that the sixteen hole repetitive pattern must be spread until it acts as an eleven hole repetitive pattern. The spacing, or the amounts of spreading, is de-l termined by the equation:

Thus it can be seen that a sixteen hole repetitive pattern must be spread until A equals 3.13K. However, it should be noted that the eleven row repetitive pattern is at optimum spacing so that maximum uniformity is maintained even though the number of effective rows the pattern acts like has been reduced. Therefore, it can be seen that a suction box having drainage openings therein spaced at intervals in accordance with the principles of the present invention will provide maximum uniform dewatering.

While I have shown and described only a single embodiment of the present invention, it will be obvious to those skilled in the art that various modifications and changes may be mad-e without departing from the invention in its broader aspect. Therefore, it is intended that the appended claims cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What I claim as new and novel and desire to secure by Letters Patent of the United States is:

1. A method for producing a suction box cover including the step of forming a plurality of drainage openings in said suction box cover at selected intervals therein, said openings being arranged and spaced in uniformly spaced parallel rows, said rows being angularly aligned with reference to the machine and cross machine direction, said openings in each of said angularly aligned rows forming parallel cross machine direction rows with adjacent openings in adjacent angularly aligned rows, said adjacent openings being spaced apart from each other in the cross machine direction =by a center to center distance of A, N of said machine direction rows forming a repetitive drainage opening pattern and said openings being of radius R, said selected intervals A being determined by the equation:

R m=N (m-l) r- 1) R2{--} :o 2 m=2 2N 2. A method as described in claim 1 wherein should A be less than 3R, then determining the spacing ANP of said openings by the equation:

3. In a structure for uniformly deliquifying a web on a traveling forming medium:

a suction box cover for contacting the undersurface of the forming medium, a plurality of drainage openings of radius R, said openings oriented in uniformly spaced parallelv rows, said rows being angularly aligned with reference to the machine and cross machine direction, said openings in each of said angularly aligned rows forming parallel cross machine direction rows with adjacent openings in adjacent angularly aligned rows, said adjacent openings being spaced from each other in the cross machine direction by a center to center distance of A, N of said cross machine direction rows of openings forming a repetitive pattern, said spacing A of said openings in the cross machine direction being determined by the equation:

4. In combination with a suction box, a suction box cover, said suction box cover having a plurality of drainage openings of radius R therein, said openings oriented in uniformly spaced parallel rows, said rows being angularly aligned with reference to the machine and cross machine directly, said openings in each of said angularly aligned rows forming parallel cross machine directly rows with adjacent openings in adjacent angularly aligned rows, said adjacent openings being spaced from each other in the cross machine direction by a center to center distance of A, N of said cross machine direction rows of said openings forming a repetitive pattern, said spacing A of said openings in the cross machine direction being determined by the equation:

5. In a papermaking machine, a suction box for uniformly dewatering a sheet-like web of water saturated material on a forming medium, said suction box including a cover having a plurality of drainage openings of radius R therein, said openings oriented in uniformly spaced lparallel rows, said rows being angularly aligned with the equation:

(rn-l) (1nl) A 2 2 N/R i 2N i-O 6. A suction box as described in claim 5 where N is equal to 3 and A is substantially equal to 2.766R.

7. A suction box as described in claim 5 wherein said spacing of said openings in the cross-machine direction is determined by the equation:

and when the solution is less than 3R, then the spacing ANP of said openings is determined by the equation:

10 where P is a whole number, is sequentially diminished References Cited from N one unit at a time until the expression UNITED STATES PATENTS 3,404,066 10/1968 Francois 162-374 E@ 5 3,097,995 7/1963 Beachler lez- 372x P l 3,136,685 6/1964 Riese et al 162--374 2,042,198 5/1936 Swauger 162--374 is made equal to or just exceeds 3R and Where Ap is determined by the equation; S. LEON BASHORE, Prlmary Examiner 10 R. H. TUSHIN, Assistant Examiner 2P ffl-2 83-13,100;162-351 NIP:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,595 747 Dated July 27, 1971 Inventor(g) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the equation set forth at column 1, line 26, column 2 line 35 and column 5, line 65, cancel "M" and "m", each occurrence, and substitute in place thereof n Column 4, line 66, "two", second occurrence, should read row Column 6, line 9, "ntsance" should read instance In the equation set forth at column 7,

line 25 and line 62, column 8, line 3, line 25, line 42, line 60 and line 68, and column 9, line 10, cancel "m",

each occurrence, and substitute n Column 7, line 30, "A", should read Ap line 59, claim l, after "said", insert cross Column 8, line l, claim 2, insert Ap after "where", same line, cancel "An".

Signed and sealed this 13th day of August 1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents ORM P04050 (HJ-59) uscoMM-Dc coen-Pee 0.5. GOVERDIMINT PIIN'I'IIIG OFFICE: IUI! Q .ICI-lll, 

